Paramyosin is a myosin-binding protein characteristic of invertebrate animals, while troponin is a Ca-dependent regulator of muscle contraction. Both proteins are widely distributed in protostomes, while in deuterostomes, their distribution is limited; namely, presence of paramyosin and absence of troponin are common features in echinoderm muscles, while muscles of chordates contain troponin but lack paramyosin. In this study, we examined the muscle of a hemichordate, acorn worm, to clarify whether this animal is like echinoderms or like the other deuterostome animals. We found a 100-kDa protein in the smooth muscle of acorn worm. This protein was identified with paramyosin, since the purified protein formed paracrystals with a constant axial periodicity in the presence of divalent cations as paramyosin of other animals, showed ability to interact with myosin and shared common antigenicity with echinoderm paramyosin. On the other hand, troponin band was not detected in isolated thin filaments, and the filaments increased myosin-ATPase activity in a Ca-independent manner. The results indicate that troponin is lacking in thin filaments of acorn worm muscle just as in those of echinoderms. The muscle of hemichordate acorn worm is quite similar to echinoderm muscles, but different from chordate muscles.

Multiblock-amphiphiles preferentially distribute in the Ld phase and encourage delocalization of cholesterol in both the Ld and Lo phases.

Connectin is the largest elastic protein that connects between Z-line and Mline of sarcomere and functions as a molecular spring of vertebrate striated muscles. In the upstream region of connectin gene, there are two genes for proteins which domain structures are closely related with that of connectin. Although RT-PCR experiments revealed that these two genes are expressed in striated muscle, their function remains unknown. In this study, we investigated the domain structures, isoforms, localizations and binding partners of these proteins in striated muscles. To know their physiological roles, we examined the effects of overexpression or knock-down of these proteins using cultured skeletal muscle cells. In this presentation, we introduce the result of our experiments. 3P140